1. Field of the Invention
The present invention relates to heat transfer systems for nuclear power generating stations, and more particularly to gas cooled nuclear power generators having a self-contained gas cooling circuit for the generation of process heat through the transfer of energy from the gas cooling circuit to a secondary circuit, and in which the high temperature reactor, the heat exchanger units, the blower, and the gas conduits between the several system components are all arranged inside a vessel of prestressed concrete (one-vessel construction).
2. Description of the Prior Art
It is known to build nuclear power generators with a self-contained gas turbine circuit as an integral unit, in which not only the reactor, but also the gas turbine, a compressor, and the heat exchanger units are arranged inside a vessel of prestressed concrete. German Offenlegungsschrift No. 2,062,934 discloses a gas cooled nuclear reactor the gas turbine of which occupies a cavity inside the wall of the pressure vessel surrounding the reactor core. Another nuclear reactor installation of similar construction is described in German Offenlegungsschrift No. 1,764,249, featuring a design in which the nuclear reactor and all the components of the cooling circuit are accommodated inside closely spaced parallel vertical bores in the concrete pressure vessel, and where the components are accessible from the outside. Conduits for the cooling medium are arranged in the wall of the pressure vessel as well as between the various bores.
It has further been suggested in a copending application to arrange the heat exchanger units inside vertical shafts or pods which are arranged in a circle around the axis of the concrete vessel, and to arrange the gas turbine unit inside a horizontal tunnel underneath the reactor core. This design further includes the suggestion of subdividing the total cooling circuit downstream of the gas turbine unit into several partial circuits of identical size. These partial circuits receive their gas flow through feeder conduits leading to separate annular-shaped channels of which each links together a group of heat exchangers.
A common feature of the reactor systems described above is that they all have a self-contained gas cooling circuit which is entirely integrated into a vessel of reinforced concrete. It is upon this basis that the present invention builds and over which various improvements are being suggested. However, the present invention and the previous designs differ in one basic aspect. Whereas the previous systems utilize the energy generated by the reactor core for the operation of a gas turbine which drives an electric generator, the system of the present invention features a cooling gas circuit from which the reactor-generated energy is transferred to a secondary circuit for the generation of process heat. Such an energy transfer arrangement in a nuclear reactor installation presupposes a sufficiently high gas temperature at the exit from the reactor core, meaning that this temperature has to be at least 850.degree. C. Such high gas temperatures, in turn, are the source of a number of problems for which no solutions are presently available in the prior art.
One major problem, for example, is the selection of suitable materials for the heat exchanger units which are subjected to a gas entry temperature of 950.degree. C. (850.degree. C. at minimum). Based upon the present state of metallurgical technology, no known materials are capable of withstanding such high temperatures over the required period of time -- the intended life of the installation is 30 years. No such problems are present for the gas exit side of the heat exchanger unit, because there, the gas temperatures are considerably lower.
Another problem relates to the thermal insulation of the installation components subjected to the high temperatures of the reactor gas cooling circuit, i.e. the primary circuit.